Technical Field
The present disclosure relates generally to the field of submerged combustion melters and apparatus, and methods of use, and more specifically to submerged combustion melters, and methods of operating same, particularly for melting glass-forming materials, mineral wool and stone wool forming materials, and other predominantly non-metallic inorganic materials.
Background Art
A submerged combustion melter (SCM) may be employed to melt glass batch and/or waste glass materials (including waste glass materials that have an organic coating) to produce molten glass, or may melt mineral wool feedstock (basalt rock, sometimes referred to as lava rock) to make mineral wool, by passing oxygen, oxygen-enriched mixtures, or air along with a liquid, gaseous and/or particulate fuel (some of which may be in one or more of the feedstock materials), directly into a molten pool of glass or other material, usually through burners submerged in a turbulent melt pool. The introduction of high flow rates of products of combustion of the oxidant and fuel into the molten material, and the expansion of the gases during submerged combustion (SC), cause rapid melting of the feedstock and much turbulence and foaming. Conventional melters operate primarily by combusting fuel and oxidant above the molten pool of melt, and are very laminar in flow characteristics compared to SCMs.
Residence time of the material being melted in the SCM is critical to achieving good quality product. Splashing of the molten vitreous mass inside the SCM is a phenomenon unique to the SCM. While aggressive mixing and turbulence are desired for reducing time to melt feedstock, this splashing (where molten material actually breaks away from the turbulent surface and travels upward and then falls back down into the vitreous mass by gravity, or strikes the ceiling or walls of the SCM and drips back down into the molten mass, or solidifies thereon) is problematic as it causes at least some of the particulate batch feed to be splashed to undesired areas within the SCM, and is thus wasteful and decreases melt quality.
In known SCMs, raw batch or other particulate material is typically fed from above the vitreous molten material in the SCM, either from feed inlets in the ceiling or the walls above the splash region, or fed by or fed by mass movers such as screws or augers through a wall with the expectation that all of the batch will penetrate into the turbulent molten mass inside the SCM, What the present inventor has discovered, however, is that the aggressive movement of the molten vitreous material causes even more violent splashing than previously recognized, causing some of the particulate materials to reach undesired areas of the SCM, such as the ceiling, reducing residence time and/or not allowing for a homogeneous melting of raw materials. Some of the batch or other particulate material may also become entrained in the exhaust gases causing additional waste. While some of this may be recycled to the feed, it is inefficient from an energy standpoint.
It would be advantageous to take advantage of the aggressive mixing and turbulence in the SCM while minimizing the disadvantages associated with splashing in order to improve the quality (mainly determined by homogeneity) and/or the quantity of the melt from an SCM.